This invention relates to an improvement of a supporting leg apparatus (hereinafter it is merely referred as a leg apparatus) which enables by means of the support wheels installed in a magnetically levitated vehicle to expand or contract freely. The improvement has been achieved, particularly aiming at the improvement of the comfortable feeling of riding, by hanging the support wheels at a certain position defined by a swing arm and a lifting actuator, and by supporting said support wheels through the action of a buffer means of the lifting actuator having a damper and a coil spring. Furthermore, with the improved lift apparatus, the support wheels can be completely retracted within a short stroking under a contraction action of the lifting actuator in which an internal lock is equipped, so that the wheel height of the vehicle can be adjusted. Moreover, the improved leg apparatus for the magnetically levitated vehicle enables the damper and coil spring to be stored inside the preventive wall which protects them from the firs and collision with foreign obstacles.
With a magnetically levitated vehicle system, the ground coil is arranged on the ground for purposes of levitation and propulsion functions, and the electrical magnets arranged on the vehicle move by forming a continuously moving magnetic field being corresponded to successive excitation of the propulsion coils. At the same time, by moving the electrical magnets on the vehicle, an inductive current is generated in the floating coil on the ground by which the magnetic field is repulsed; and this in turn results in floating vehicle.
However, only when a sufficient speed is attained by the vehicle does the inductive magnetic levitating force generate an amount of power which is enough to support the full weight of the vehicle; as a result additional wheels are required to support the vehicle at a low cruising speed.
Such a supporting apparatus with wheels should be expected to operate the vehicle comfortably when the vehicle is at rest or at necessitated low speed range; while in case of high speed range, it should be retracted and stored within the vehicle body. Furthermore, when the wheels are needed, they should be extended from the vehicle body and a certain mechanism is required to absorb the shock while the wheels are in an extending position.
A prior art leg supporting apparatus employed in a magnetically levitated vehicle (Tokkai-Sho No. 63-212165) disclosed a structure in which wheels were supported by means of a trailing arm on which a damper was installed to act as a shock absorber. Furthermore, a lift cylinder was installed at a pivot side of the damper to retract the wheels when the damper and the trailing arm are lifted.
With a structure of the aforementioned support wheels, an impact generated while the wheels are expanding is supposed to be absorbed through a damper on the trailing arm. However, since the damper utilized in the structure is principally an oil/air type, a packing seal is employed on the piston for leak-proof of oil or air. Consequently, the friction caused by the seal is high while the piston is in an operation stage, so that a proper movement has a tendency to be delayed. As a result, further improvement in riding comfort cannot be achieved.
Moreover, in the U.S. Pat. No. 5,058,916 an apparatus for supporting an expandable and contractible base wheel which had been basically used for a highway or railroad is disclosed. The apparatus is constructed by connecting one end of a trailing arm that is provided at a shaft of the wheels to a flexible cable of a rubber air spring as a first lifting means and by providing a buffer device between the air spring as the first lifting means and the trail arm. By means of the aforementioned construction, the wheels can be moved vertically by supplying or exhausting a pressurized air to the air spring of the first lifting means and the air spring of the second lifting means.
The apparatus for supporting base wheel disclosed in U.S. Pat. No. 5,058,916 requires two lifting means, and this in fact represents a complicated structure. The ride is not expected to be comfortable because of the existance of a hysteresis action that is caused by the air spring. Moreover, fractures of the rubber air spring or the flexible cable could occur. Hence it is difficult to adopt the apparatus for use as a leg supporting for a high speed running magnetically levitated vehicle.
Furthermore, UK Patent No. 2,134,052 discloses a supporting apparatus for an amphibian vehicle. With this supporting apparatus, one end of the lever arm which is rotatable along a rotating shaft installed to a vehicle bracket is supported rotatably to a driving shaft of the cylinder that is connected to the vehicle bracket at one end. Furthermore, the other end of lever arm is provided rotatably to a rotating shaft through a buffer device. Moreover of the driving shaft, driven by pressure generated from supplied oil to the cylinder, rotates the lever arm along the rotating shaft, and this consequently causes the wheels to move in vertical direction.
The apparatus for a base wheel (disclosed in UK Patent No. 2,134,052) requires many components and four plates to be installed to the main vehicle, and this results in making the device structurally a complicated one. Besides, the buffer device is constructed to have an enclosed pressurized air which tends to exhibit a large hysteresis; hence the ride is not expected to be comfortable. This is a technical drawback associated with the patent.
Furthermore, since passengers get on and off from the magnetically levitated vehicle while it is at rest, the leg apparatus for supporting wheels should be adjusted so that it maintains an even level for the accommodation of a certain height of a platform.
When the vehicle weight is altered after the completion of manufacturing the vehicle or due to demand to change the vehicle height due to unexpected changes in number of passengers, an improved leg apparatus is needed to correspond easily to such occasional fluctuations. Moreover, to the best knowledge of the present applicants, there is no single leg apparatus proposed which is designed and constructed to maintain the original function thereof even under any of the expected accidental circumstances including collision of foreign obstacles from the road against the leg apparatus, which leads to damage of the spring or other components while cruising at a low speed, or catching fire due to excess heat on the braking device that results from the collision of flammable foreign obstacles.